The present invention relates to a method and apparatus for treating electrically conductive fluid, that is fluid having some electroconductive capability. More particularly, the present invention relates to a method and apparatus utilizing a capacitive effect for ionizing water having a high mineral content to prevent the precipitation of solids from the water which would tend to form a scale on the inner surface of piping through which the water flows, and to aid in the removal of a previously formed scale.
It has been known in the past to use chemicals for cleaning a scale from fluid piping, which scale was formed by the deposition of the soluble content of the fluid passing through the piping. However, the waste products of such chemical treatment are becoming hazardous to the ecology, and give rise to other harmful effects. Therefore, many methods and apparatus which do not use chemicals have been developed for the treatment of fluid, and which methods and apparatus give rise to no residual harmful effects. Such systems typically employ magnetic or electric energy to treat the fluid.
In the systems employing electric energy, electrodes having different electrochemical potentials are employed, and a resistor is connected between the electrodes. The fluid to be treated is passed between the electrodes and in direct contact therewith. The resistor is employed as a current control device so as to establish an appropriate electroconductive connection between the electrodes through the electroconductive fluid to be treated, whereby the fluid becomes ionized.
However, all of the known non-chemical systems for treating fluid possess a degree of unreliability due to wide variations in the conditions of the fluid to be treated, such as the electroconductivity of the fluid, soluble content of the fluid, pH, etc.
The present inventor has conducted research into the development of non-chemical fluid treatment apparatus and methods using a pair of electrodes having different electrochemical potentials to ionize fluid.
In conducting such research, the present inventor has carried out tests which illustrate that when electric current flowing through the fluid to be treated and between the electrodes is reduced, there is an improvement in the ability of the device to prevent the precipitation of solids (Ca, Mg and Si) dissolved in the fluid and thus prevent the formation of a scale, particularly a silica scale which is the most difficult type of scale to prevent. In such tests, it was observed that the precipitation of Ca, Mg and Si particles commences very early when there was a direct electrical connection between the electrodes, i.e. maximum current flow. When the resistance between the electrodes was increased to successively reduce the electric current flow, it was observed that the precipitation of the Ca, Mg and Si particles became further and further delayed along with a corresponding reduction in the amount of precipitative material and hence a reduction in the formation of a crystalline scale. As these tests were continued, and the values of resistance was increased to reduce the electric current flow, the formation of a Ca, Mg and Si precipitate ceased and only a colloidal suspension was observed. And, with an even further increase in resistance between the electrodes, even the colloidal suspension began to form more slowly and then only in water having a high degree of hardness and greater electroconductive capability. Such tests are disclosed in more detail in copending appln. U.S. Ser. No. 07/556,170 filed Jul. 20, 1990.
However, with an increase in electroconductivity of the fluid to be treated, there is a corresponding increase in the current flow between the electrodes. Accordingly, it follows that fluids with a high electroconductive capability are very difficult to effectively treat with such systems because they give rise to a relatively high electric current flow resulting in an accompanying lowering of the efficiency of the system.
Thus, in a unique embodiment featured in U.S. Pat. No. 4,902,391 by the present inventor, the electroconductive connection between the electrodes was only established by the fluid to be treated extending therebetween, thereby providing a structure in which minimum current flow and maximum potential difference between the electrodes was expected.
The present invention, representing a development from the above-described patented and pending devices, is drawn to a method and apparatus for treating even fluid having a high electroconductive capability by relying on the relationship found by the present inventor between the degree of effectiveness of the fluid treatment and the amount of current flow through the fluid as produced by the device. More specifically, the present invention is the result of research by the present inventor into means of further restricting electric current flow through the fluid to be treated so as to arrive at an appropriate method and apparatus for treating fluids having various electroconductive capabilities, even very high electroconductive capabilities.